1. Field of the Invention
This invention relates to a method for preparing phytin and related products including inositol and phytic acid.
2. Discussion of the Background
Phytin is a calcium magnesium salt of phytic acid. It is distributed in almost all parts of plant tissue, especially in seeds. It is an important source for producing inositol or phytic acid, both of which are used in the food industry. Phytic acid is a hexaphosphoric acid ester of inositol. It has a chelating action by which trace metals in foodstuffs are inactivated, preventing the discoloration and deterioration of foodstuffs.
Inositol is also called mesoinositol or myoinositol. It is contained in plants as a component of phytin, and is found in the free state in animal tissues such as muscle, heart, liver, etc. Inositol is also a component of phosphatides which is widely distributed in natural organisms, especially in mammalian liver and brain, egg yoke, soybean and wheat germ. It is important as a vitamin in the higher animals and performs an important role in the metabolism of fats and cholesterol. A number of studies have shown its lipotropic function, and its effect on cirrhotic livers and hyper-cholesteremia. Inositol has therefore recently become an important substance in the field of health foods in the United States and the other countries.
Inositol is usually produced from raw materials such as rice bran or corn steep liquor. For example, rice bran may be treated with an organic or inorganic acid to extract phytin. Phytin is then precipitated and separated from the extract, usually by filtration, to remove unwanted proteins and carbohydrates. The separated phytin is then hydrolyzed under pressure to recover inositol, which is further purified, concentrated, and crystallized. In this method, organic solvents, water-soluble metallic salts such as iron chloride, manganese sulfate, and water-soluble alkaline substances such as sodium hydroxide, aqueous ammonia, may be employed as precipitants for phytin. However, phytin usually precipitates as a colloidal, pasty substance when these precipitants are used, rendering satisfactory elimination of impurities extremely difficult.
Phytin may also be precipitated with calcium compounds such as calcium phytate. However in this case a large amount of proteinous, difficult to remove, impurities co-precipitate. Calcium phytate itself precipitates as a pasty crystallized mass. This often causes process problems, such as blocking of the nozzles of centrifugal separator during the operation. And a large amount of fine crystallized calcium phosphate forms as a by-product after the phytin hydrolysis step. A considerable amount of inositol is thus lost in this crystalline material in the successive inositol-calcium phosphate separating step, resulting in an unavoidable economic disadvantage due to a decrease in inositol recovery. The separated calcium phosphate is also unsatisfactory from an economical viewpoint due to its low purity.
There is thus a strongly felt need for a facile process for the production of phytin and related products in high yields and in high degrees of purity.